1. Field of the Invention
The present invention relates to a wireless communication terminal capable of selecting an optimum communication system from a plurality of communication systems, and a communication system selection method for selecting an optimum communication system.
2. Description of Related Art
There has been known a multi-mode terminal that selectively adopts a plurality of wireless communication systems. With use of such a multi-mode terminal, the same terminal can be used for communication in areas different in wireless communication system. In any area where a plurality of wireless communication systems are available, the multi-mode terminal selects any optimum system for communication.
For example, a multi-mode wireless communication device disclosed in JP-A-2007-116672 refers to, in selection of the communication system, a switching power needed for switching communication systems, and a power consumption required for communication in each of the communication systems. Numerical values of such switching power and power consumption are stored in advance as coefficients in a separately-provided storage section. The numerical values of the power consumption are stored as the power consumption per unit time, and such values are multiplied by the communication time for use as evaluation values.
Also, a communication terminal device disclosed in JP-A-2008-11452 uses power consumption information that is managed in detail in a power value management table, in switching the communication systems. The power value management table manages various values of power, e.g., power on standby, power for a voice call, communication speed and power for packet communication, power of an RF section during control over power for transmission, power of the RF section and that of a baseband section during intermittent reception, and power associated with audio encoding. Such information helps to select the most power-efficient communication system according to the circumstances.
with use of the technologies disclosed in the above Patent Documents, the most power-efficient communication system can be selected at each stage. However, in such technologies, there is no provision of an evaluation value related to a data rate that can be implemented by each of the communication systems. In this sense, even if the selected communication system is power efficient, the communication system may not satisfy requirements in view of capabilities in some cases. Moreover, as not giving consideration to information about the remaining level of battery, the above technologies are not ready for a case of applying a high data rate even if the power supply is ample, and even if the power consumption is increased.
When the a multi-mode terminal selects any optimum wireless communication system, a data rate serves as a significant indicator in addition to the power consumption of each of wireless communication systems available for use. For example, reserving a wide range in a high frequency band enables higher-speed wireless communication, however, an extreme increase of the power consumption is not considered preferable. On the other hand, reducing the data rate can indeed reduce the power consumption, but this fails to ensure a required level of data rate, thereby possibly resulting in a failure of services or an increase of the eventual power consumption due to the communication forced to be very long.
The invention is proposed in consideration of such circumstances, and an object thereof is to provide a wireless communication terminal that can select a power-efficient wireless communication system while keeping a data rate at a standard level determined by the remaining level of power and a communication history, and a communication system selection method.